Near-simultaneous He ii \(\) 1640 and \(\) 4686 fluxes have also been reported from the 2013 AGNSTORM campaign by [1]} and [2]} respectively. The uncorrected values as reported are shown as the open circles in Figure 4. Taken at face value these straddle the theoretical ratio and this could be taken as evidence for no reddening. However, whilst [2]} subtracted out broad optical Fe ii emission from He ii \(\) 4686, [1]} did not subtract out the substantial O iii] \(\) 1663 contribution from He ii \(\) 1640. As explained above O iii] \(\) 1663 will be much less variable than He ii and will not follow rapid variations of the continuum the way He ii does. For display purposes, to again emphasize that what matters is the slope, we have subtracted off a constant flux of \(500 \times 10^{-15}\)  ergs s\(^{-1}\)  cm\(^{-2}\)  from the reported He ii \(\) 1640 fluxes to make the OLS-bisector line go through the origin. These points are shown as filled circles in Figure 4. Again, the subtraction of a constant has no effect on our reddening estimate which depends only on the slope of the line. The slope of the OLS-bisector fit gives a mean He ii \(\) 1640/\(\) 4686 ratio of \(3.44 \pm 0.055\)  and hence \(E(1640-4686)\)  of \(0.98 \pm 0.24\) . Our method thus gives a similar mean reddening for the 2013 AGNSTORM campaign as for the 1988-1989 observing campaign even though the He ii flux levels were higher in 2013.
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